/**
 * FreeRTOS Kernel V10.5.1
 * Copyright (C) 2021 Amazon.com, Inc. or its affiliates.  All Rights Reserved.
 *
 * SPDX-License-Identifier: MIT
 *
 * Permission is hereby granted, free of charge, to any person obtaining a copy of
 * this software and associated documentation files (the "Software"), to deal in
 * the Software without restriction, including without limitation the rights to
 * use, copy, modify, merge, publish, distribute, sublicense, and/or sell copies of
 * the Software, and to permit persons to whom the Software is furnished to do so,
 * subject to the following conditions:
 *
 * The above copyright notice and this permission notice shall be included in all
 * copies or substantial portions of the Software.
 *
 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
 * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS
 * FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR
 * COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER
 * IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN
 * CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
 *
 * https://www.FreeRTOS.org
 * https://github.com/FreeRTOS
 *
 */

/* -----------------------------------------------------------
 * Implementation of functions defined in portable.h for the RISC-V port.
 *---------------------------------------------------------- */

/* Scheduler includes. */
#include "FreeRTOS.h"
#include "task.h"
#include "portmacro.h"

/* Standard includes. */
#include "string.h"

#ifdef configCLINT_BASE_ADDRESS
    #warning The configCLINT_BASE_ADDRESS constant has been deprecated.  configMTIME_BASE_ADDRESS and configMTIMECMP_BASE_ADDRESS are currently being derived from the (possibly 0) configCLINT_BASE_ADDRESS setting.  Please update to define configMTIME_BASE_ADDRESS and configMTIMECMP_BASE_ADDRESS dirctly in place of configCLINT_BASE_ADDRESS.  See https://www.FreeRTOS.org/Using-FreeRTOS-on-RISC-V.html
#endif

#ifndef configMTIME_BASE_ADDRESS
    #warning configMTIME_BASE_ADDRESS must be defined in FreeRTOSConfig.h.  If the target chip includes a memory-mapped mtime register then set configMTIME_BASE_ADDRESS to the mapped address.  Otherwise set configMTIME_BASE_ADDRESS to 0.  See https://www.FreeRTOS.org/Using-FreeRTOS-on-RISC-V.html
#endif

#ifndef configMTIMECMP_BASE_ADDRESS
    #warning configMTIMECMP_BASE_ADDRESS must be defined in FreeRTOSConfig.h.  If the target chip includes a memory-mapped mtimecmp register then set configMTIMECMP_BASE_ADDRESS to the mapped address.  Otherwise set configMTIMECMP_BASE_ADDRESS to 0.  See https://www.FreeRTOS.org/Using-FreeRTOS-on-RISC-V.html
#endif

/* Let the user override the pre-loading of the initial RA. */
#ifdef configTASK_RETURN_ADDRESS
    #define portTASK_RETURN_ADDRESS    configTASK_RETURN_ADDRESS
#else
    #define portTASK_RETURN_ADDRESS    0
#endif

/* The stack used by interrupt service routines.  Set configISR_STACK_SIZE_WORDS
 * to use a statically allocated array as the interrupt stack.  Alternative leave
 * configISR_STACK_SIZE_WORDS undefined and update the linker script so that a
 * linker variable names __freertos_irq_stack_top has the same value as the top
 * of the stack used by main.  Using the linker script method will repurpose the
 * stack that was used by main before the scheduler was started for use as the
 * interrupt stack after the scheduler has started. */
#ifdef configISR_STACK_SIZE_WORDS
__attribute__((aligned(16))) StackType_t xISRStack[ configISR_STACK_SIZE_WORDS ] = { 0 };
/* const StackType_t xISRStackTop = (StackType_t) & (xISRStack[ configISR_STACK_SIZE_WORDS & ~portBYTE_ALIGNMENT_MASK ]); */
StackType_t xISRStackTop = 0;

/* Don't use 0xa5 as the stack fill bytes as that is used by the kernerl for
the task stacks, and so will legitimately appear in many positions within
the ISR stack. */
#define portISR_STACK_FILL_BYTE    0xee
#else
extern const uint32_t __freertos_irq_stack_top[];
const StackType_t xISRStackTop = (StackType_t) __freertos_irq_stack_top;
#endif

/**
 * Setup the timer to generate the tick interrupts.  The implementation in this
 * file is weak to allow application writers to change the timer used to
 * generate the tick interrupt.
 */
void vPortSetupTimerInterrupt(void) __attribute__((weak));

/* ----------------------------------------------------------- */

/* Used to program the machine timer compare register. */
uint64_t ullNextTime = 0ULL;
/* const uint64_t *pullNextTime = &ullNextTime; */
const size_t uxTimerIncrementsForOneTick = (size_t)((configCPU_CLOCK_HZ) / (configTICK_RATE_HZ));          /* Assumes increment won't go over 32-bits. */
uint32_t const ullMachineTimerCompareRegisterBase = configMTIMECMP_BASE_ADDRESS;
volatile uint64_t *pullMachineTimerCompareRegister = NULL;
uint64_t ullStartTime = 0ULL;
/* Holds the critical nesting value - deliberately non-zero at start up to
 * ensure interrupts are not accidentally enabled before the scheduler starts. */
size_t xCriticalNesting = (size_t) 0xaaaaaaaa;
size_t *pxCriticalNesting;

/* Used to catch tasks that attempt to return from their implementing function. */
size_t xTaskReturnAddress = (size_t) portTASK_RETURN_ADDRESS;

/* Set configCHECK_FOR_STACK_OVERFLOW to 3 to add ISR stack checking to task
 * stack checking.  A problem in the ISR stack will trigger an assert, not call
 * the stack overflow hook function (because the stack overflow hook is specific
 * to a task stack, not the ISR stack). */
#if defined( configISR_STACK_SIZE_WORDS ) && ( configCHECK_FOR_STACK_OVERFLOW > 2 )
#warning This path not tested, or even compiled yet.

static const uint8_t ucExpectedStackBytes[] = {
    portISR_STACK_FILL_BYTE, portISR_STACK_FILL_BYTE, portISR_STACK_FILL_BYTE, portISR_STACK_FILL_BYTE,        \
    portISR_STACK_FILL_BYTE, portISR_STACK_FILL_BYTE, portISR_STACK_FILL_BYTE, portISR_STACK_FILL_BYTE,        \
    portISR_STACK_FILL_BYTE, portISR_STACK_FILL_BYTE, portISR_STACK_FILL_BYTE, portISR_STACK_FILL_BYTE,        \
    portISR_STACK_FILL_BYTE, portISR_STACK_FILL_BYTE, portISR_STACK_FILL_BYTE, portISR_STACK_FILL_BYTE,        \
    portISR_STACK_FILL_BYTE, portISR_STACK_FILL_BYTE, portISR_STACK_FILL_BYTE, portISR_STACK_FILL_BYTE
};
\

#define portCHECK_ISR_STACK() configASSERT( ( memcmp( ( void * ) xISRStack, ( void * ) ucExpectedStackBytes, sizeof( ucExpectedStackBytes ) ) == 0 ) )
#else
/* Define the function away. */
#define portCHECK_ISR_STACK()
#endif /* configCHECK_FOR_STACK_OVERFLOW > 2 */

/* ----------------------------------------------------------- */

#if( configMTIME_BASE_ADDRESS != 0 ) && ( configMTIMECMP_BASE_ADDRESS != 0 )

void vPortSetupTimerInterrupt(void)
{
    uint32_t ulCurrentTimeHigh, ulCurrentTimeLow;
    volatile uint32_t *const pulTimeHigh = (volatile uint32_t *const)((configMTIME_BASE_ADDRESS) + 4UL);          /* 8-byte type so high 32-bit word is 4 bytes up. */
    volatile uint32_t *const pulTimeLow = (volatile uint32_t *const)(configMTIME_BASE_ADDRESS);
    volatile uint32_t ulHartId;

    __asm volatile("csrr %0, mhartid" : "=r"(ulHartId));
    pullMachineTimerCompareRegister  = (volatile uint64_t *)(ullMachineTimerCompareRegisterBase + (ulHartId * sizeof(uint64_t)));

    do {
        ulCurrentTimeHigh = *pulTimeHigh;
        ulCurrentTimeLow = *pulTimeLow;
    } while (ulCurrentTimeHigh != *pulTimeHigh);

    ullStartTime = (uint64_t) ulCurrentTimeLow | (uint64_t) ulCurrentTimeHigh << 32;
    ullNextTime = (uint64_t) ulCurrentTimeHigh;
    ullNextTime <<= 32ULL; /* High 4-byte word is 32-bits up. */
    ullNextTime |= (uint64_t) ulCurrentTimeLow;
    ullNextTime += (uint64_t) uxTimerIncrementsForOneTick;
    *pullMachineTimerCompareRegister = ullNextTime;

    /* Prepare the time to use after the next tick interrupt. */
    ullNextTime += (uint64_t) uxTimerIncrementsForOneTick;
}

#endif /* ( configMTIME_BASE_ADDRESS != 0 ) && ( configMTIME_BASE_ADDRESS != 0 ) */
/* ----------------------------------------------------------- */

BaseType_t xPortStartScheduler(void)
{
    extern void xPortStartFirstTask(void);

    pxCriticalNesting = &xCriticalNesting;
    xISRStackTop = (StackType_t) & (xISRStack[ configISR_STACK_SIZE_WORDS & ~portBYTE_ALIGNMENT_MASK ]);

#if( configASSERT_DEFINED == 1 )
    {
        /* Check alignment of the interrupt stack - which is the same as the
         * stack that was being used by main() prior to the scheduler being
         * started. */
        configASSERT((xISRStackTop & portBYTE_ALIGNMENT_MASK) == 0);

#ifdef configISR_STACK_SIZE_WORDS
        {
            memset((void *) xISRStack, portISR_STACK_FILL_BYTE, sizeof(xISRStack));
        }
#endif /* configISR_STACK_SIZE_WORDS */
    }
#endif /* configASSERT_DEFINED */

    /* If there is a CLINT then it is ok to use the default implementation
     * in this file, otherwise vPortSetupTimerInterrupt() must be implemented to
     * configure whichever clock is to be used to generate the tick interrupt. */
    vPortSetupTimerInterrupt();

#if( ( configMTIME_BASE_ADDRESS != 0 ) && ( configMTIMECMP_BASE_ADDRESS != 0 ) )
    {
        /* Enable mtime and external interrupts.  1<<7 for timer interrupt,
         * 1<<11 for external interrupt.  _RB_ What happens here when mtime is
         * not present as with pulpino? */
	__asm volatile("csrs mie, %0" :: "r"(0x10880));
    }
#endif /* ( configMTIME_BASE_ADDRESS != 0 ) && ( configMTIMECMP_BASE_ADDRESS != 0 ) */

    xPortStartFirstTask();

    /* Should not get here as after calling xPortStartFirstTask() only tasks
     * should be executing. */
    return pdFAIL;
}
/* ----------------------------------------------------------- */

void vPortEndScheduler(void)
{
    /* Not implemented. */
    for (;;);
}
/* ----------------------------------------------------------- */

void vPortTimeUpdate(void)
{
    volatile uint32_t *const pulTimeHigh = (volatile uint32_t *const)((configMTIME_BASE_ADDRESS) + 4UL);
    volatile uint32_t *const pulTimeLow = (volatile uint32_t *const)(configMTIME_BASE_ADDRESS);
    volatile uint32_t *pulTimeCompare = (volatile uint32_t *)pullMachineTimerCompareRegister;
    volatile uint32_t *const pulTimeLowCompare = pulTimeCompare;
    volatile uint32_t *const pulTimeHighCompare = pulTimeCompare + 1;
    uint64_t t = ((uint64_t) * pulTimeHigh << 32) | (*pulTimeLow);
    t += 100;
    if (t < ullNextTime) {
        *pulTimeLowCompare = -1;
        *pulTimeHighCompare = ullNextTime >> 32;
        *pulTimeLowCompare = ullNextTime & 0xffffffff;
    }
    ullNextTime += uxTimerIncrementsForOneTick;
}

unsigned long long vPortGetSchedulerNSClock_Raw(void)
{
    volatile uint32_t *const pulTimeHigh = (volatile uint32_t *const)((configMTIME_BASE_ADDRESS) + 4UL);
    volatile uint32_t *const pulTimeLow = (volatile uint32_t *const)(configMTIME_BASE_ADDRESS);
    uint64_t ullTime;
    uint32_t ulCurrentTimeHigh, ulCurrentTimeLow;
    do {
        ulCurrentTimeHigh = *pulTimeHigh;
        ulCurrentTimeLow = *pulTimeLow;
    } while (ulCurrentTimeHigh != *pulTimeHigh);

    ullTime = (uint64_t)ulCurrentTimeLow + ((uint64_t)ulCurrentTimeHigh << 32);
    return (ullTime - ullStartTime) * 1000ULL / (configCPU_CLOCK_HZ / (1000 * 1000ULL));
}
unsigned long long vPortGetSchedulerNSClock(void)
{
    uint64_t ns;
    taskENTER_CRITICAL();
    ns = vPortGetSchedulerNSClock_Raw();
    taskEXIT_CRITICAL();
    return ns;
}
